This invention relates to boat hulls generally, and more particularly to planing type hulls. Planing type hulls are designed to move generally over the water rather than through it, as do displacement type hulls. Planing can be defined as that stage at which dynamic forces due to the motion of the hull through the water begin to make their influence felt.
Many hulls have in the past been designed to decrease the resistance of the hull moving through or over the water, and also to increase the directional stability of the hull while moving through or over the water. Attempts to achieve both of these objectives have been compromises because of the problems involved. To decrease the resistance to movement of the boat, the most desired form of hull is a flat plane since it draws the least water for its weight. The flat bottom type hull is a classic example of a planing type hull which tends to climb above the water to a full planing position from its in-the-water displacement position while at rest. However, the flat bottom hull lacks directional stability and pounds badly in choppy seas.
On the other hand, the most stable and softest riding hull in rough or choppy water is the deep V hull. The deep V hull usually has three or more lift or stability strakes running fore and aft on each side of the bottom. These trap air under the bottom so that the hull will ride on bubbles, thus reducing the displacement somewhat. The deep V hull generally lacks lateral stability. The reentry of the deep V hull in choppy water is stern first, because of the weight distribution, and because the sharp V cleaves the water for a softer landing. However, the deep V hull provides considerably more frontal resistance than the planing hull, thus resulting in considerable loss of planing performance. Moreover, even the deep V type hull is unstable in waves or choppy water when the hull direction is at an angle, that is, not perpendicular to the waves, thus giving rise to the tendency to side slip or tip over.
Attempts to alleviate the problem of the tendency of the deep V hull to side slip or tip over in turning situations have resulted in utilization of multi-hulls, also known as multiple-keel hulls. The side stabilizers of a multiple-keel hull are generally of the V type, and hence have the disadvantage of relatively high frictional resistance since they are not capable of planing. Various hulls are used for certain applications. For example, the cathedral tri-hulls have added lateral stability and greater load carrying capabilities. The cross-section of a cathedral hull looks like a deep V in the middle with shallower Vs on each side. The riding qualities depend primarily on the center deep V. The side Vs trap air and run it under the hull, and cause the hull to run flat in a turn by propping up the usual deep V tendency to bank. The great advantages are stability (especially at slow speeds) and additional load carrying capability.
While the tunnel hull is essentially a planing type hull, it lacks desired directional stability. The crosssection of a tunnel hull looks like a deep V sawed with a flat horizontal section in the middle. The rush of trapped air in the tunnel helps provide dynamic lift. The advantage of the tunnel hull is great speed, while the principal disadvantages are the relatively high power needed and the low load carrying capability. Rough water performance is moderately good.
None of the hulls discussed above have incorporated a dihedral tunnel concept by means of a biplanar central hull portion with optimally deeper outside floats. Some quasi-hydro hulls have utilised a shallower central hull, but those designs were unstable in turns and in rough water; applicant believes the instability was due to the small difference in depth between the outer sponsons and the central hull.
It is believed that the ultimate in a boat hull design would be a planing type hull with absolute directional and lateral stability. It would be desirable to provide a boat hull which would at least approximate the performance of a planing type hull, and at the same time provide for a high degree of directional stability and rough water performance. This invention provides such a boat hull.
More specifically, it is desired to provide a softer, smoother ride on and over rough water, with comfort and safety at speeds in excess of 30 mph, and to provide greater load carrying capabilities and additional usuable space. It is also desired to provide a hull configuration that will get the boat out of and on top of the water with a reduction of frontal resistance by means of a reduction of wetted surface, thus providing minimal resistance with greater efficiency to both hull and power drive.
Further, it is desired to relieve the shock impact of reentry of such a hull in rough and choppy water, and hence to provide smooth forward motion. It is also desired to provide improved stability through the incorporation of integral twin floats.
These features and others which will become apparent when reference is made to the following description and accompanying drawings are provided by this invention.
It is believed that achieving the objective of smoother ride in rough water requires the utilization, at least to some extent, of the V type hull. Historically, hull designs in which the V type hull was employed have resulted in considerable loss of the planing characteristic, and hence, considerable increase in longitudinal resistance. Employment of the V type hull in combination with other hull forms is a compromise, with the objective of solving the problems of substantial frontal resistance of V type hulls, and substantial directional instability and pounding of planing type hulls. The subject invention is likewise such a compromise. However, the resulting performance is substantially better than that obtained by previous hulls.